Process and apparatus for determining the presence



March 3, 1964 c, CLARK, JR 3,123,067

PROCESS AND APPARATUS FOR DETERMINING THE PRESENCE OF FOREIGN SUBSTANCES IN THE BLOOD STREAMS OF LIVING ANIMALS Filed Aug. 1, 1960 2 Sheets-Sheet 1 Hl/manar-y left l/entr/c/e INVENTOR. Leland c. Clam Jn f f/i ww United States Patent Office Patented Mar. 3, 1%64 PROCE AND APPARATUS FGR DETERMENING THE PRESENCE F FOREIGN SUBSTAPJQES IN THE B1001) STREAM (3F LRTNG ANIMALS Leland C. Clark, 31"., 2504 Kingswood Road, Birmingham 9, Ala. Filed Aug. 1, 1969, Ser. No. 46,501 12 lilainrs. (til. 128-2.!)5)

This invention relates to a process for determining at a desired location in the blood stream or tissue of living animals, the presence thereat of a foreign substance which has been purposely placed in the blood stream at a different location from the place under investigation.

Viy invention thus contemplates, generally, the provision of a suitable, reliable and accurate process and apparatus for determining the presence of certain foreign substances in the blood stream of living animals, and contemplates such determinations for the purpose of various medical diagnoses.

My invention relates particularly to a process for determining the presence of defects in the septum of an animal heart, namely, to detect the presence of left to right shunts as an aid in the diagnosis of congential heart disease in humans.

My invention also contemplates an improved catheterborne electrode effective, when employed as herein disclosed, to give an electric signal indicative of the presence of such shunt.

In diagnosing ailments of humans, such for instance as the presence of left to right shunts in the heart, it is desired to determine not only the presence of the efect in the septum, but often the extent thereof. In investigations of the circulatory system in general it is desirable to determine both time-wise and quantity-wise the flow of blood from the heart to various parts of the body.

My invention proposes the process for performing such diagnoses which includes the steps of inserting directly into the blood vessels or the heart itself a catheter-borne electrode which is sensitive to a purposefully inhaled or injected non-toxic substance, whereby such electrode produces a signm indicative of the presence of such material in the area of the electrode.

In the diagnosis of shunts in the heart septum of humans, it has heretofore been the practice to draw blood samples which are analyzed for the presence of a purposely inhaled foreign gas or the like. Such a technique has the disadvantages of time delay and inaccuracy, and the usual debilitating effects on the patient of blood letting. Further, with such prior procedure it is difiicult to determine the extent of the shunt and impossible to determine the exact location of the opening in the septum.

In view of the foregoing another object to my invention is to provide a process and apparatus especially adapted for carrying out said process for determining, directly from the interior of the suspect chamber of the heart, usually the right heart cham er, the presence therein of blood containing a purposely inhaled or intravenously injected foreign material, thereby to obtain continuous and accurate signals indicative of the extent and location of the defect in the septum.

Another object is to provide a process of the character designated in which the signal from the right heart chamber is continuously correlated with a signal obtained from the inhalation or injection of the foreign gas or substance, thus to present to the operator a continuous indication of the intake of such substance as compared with the amount indicated as being present in the right heart chamber.

Another object. is to provide apparatus for carrying out my improved process embodying an electrode mounted on the entrance end of a cathode and which 2; gives a signal in the presence of the foreign gas or material, together with means to mount the electrode preferably in electrically insulated relation to a catheter proper, thereby providing a current path leading externally of the body.

Apparatus illustrating the constructional features of my invention and which may be used to carry out my im proved process is shown in the accompanying drawing, forming a part of this application, in which:

FIG. 1 is a longitudinal sectional view partly broken away of a catheter having mounted thereon my improved electrode;

FIG. 2 is a wholly diagrammatic view of a human body illustrating the manner of carrying out my improved process;

FIG. 3 is a wholly diagrammatic view illustrating the airway catheter in position in the nose of the patient;

FIG. 4 is a wholly diagrammatic view of a human heart having a septal defect and showing some typical examples of signals obtained from the interior of the various heart chambers by means of my improved process and apparatus; and,

FIG. 5 is a chart showing the flow of blood in the normal human heart in full lines with certain defects indicated in broken lines thereon.

l eferring now to the drawings for a better understanding of my invention and more particularly to FIG. 1, I show a catheter-borne electrode which comprises a catheter-borne electrode which comprises a catheter proper indicated at It and which may be in the form of a tube. At its outer end the tube may carry an internally threaded member 11 to which may be attached a blood sampling device or a blood pressure indicator.

At the entrance end 12 of the catheter I place a small electrode 13. It will be noted that the electrode is insulated from the end of the catheter 10 by means of an electrically insulating cover 14. Further, a conductor 16 is electrically connected to the rear end of the electrode 13 and the conductor 16 is insulated from the tube 10 by insulation indicated at 17. The insulated conductor 16 emerges from the catheter tube Jill through a sealed neck 13, located at a point to be always external of the body.

The outer or rounded end 13 of the electrode 13 is so constructed as to be sensitive to hydrogen. That is, the portion 13 will, in the presence of hydrogen, generate an electric signal. While there may be various ways of preparing such an electrode I prefer to use an electrode made of platinum in which the area 13 is coated with platinum black by placing it in a 5% solution of platinic chloride and connecting the lead wire to a source of 1.5 volts, such as a flashlight battery. A piece of platinum Wire is placed in the platinizing solution to serve as the anode. Plating is continued for about a minute, or until the platinum tip is perceptibly gray. Also, an electrode corresponding to 13* made of palladium is satisfactory. Either platinum or palladium may be alloyed with a metal such as iridium or the like to provide a suitable electrode. Likewise, coatings of palladium black, palladium or platinum or other metals are satisfactory.

It Will be noted, also, that the catheter 16 may have holes 19 in its inner end. The purpose of this is to permit blood to flow into the catheter tube for the purpose of removing it from the outer end if desired.

Referring now particularly to FIGS. 2 and 3 I show in diagrammatic manner the method of carrying out my improved process and using the catheter shown in FIG. 1. First, I insert in the nose of the patient a nasal catheter 21 having thereon a tip 22 prepared substantially identically as electrode 13. If desired, one of the electrodes 22 may be placed in each nostril and connected in parallel. The catheter 21 is held in place on the nose of the patient by means of a piece of adhesive plaster or the like indicated at 23. In placing the catheter it is important that the tip 22 be in contact with moist tissue. Connected to the tip 22 is an electric conductor 24.

At some suitable point on the skin of the patients body I place a reference electrode 26. This electrode may be a sheet of silver and preferably is brought into contact with the skin through a saline soaked pad or with ECG electrode paste. As will presently appear, other types of skin reference electrodes may be used, since the type of skin electrode used only affects the initial (before hydrogen administration) potential.

As shown in FIG. 2, a wire 27 from the electrode 26 leads to a voltmeter 28. The wire 24 from the nasal electrode 22 leads also to the voltmeter 28. The lead 15 from the electrode 13 may lead to a second voltmeter 29 and the two voltmeters may be cross connected by a wire 31.

In FIG. 2 I indicate the heart in wholly diagrammatic form as embodying the capillaries indicated by the block 32; the septum by the numeral 33 and having a defect 33* therein; the left ventricle at 34; the right ventricle at 35; the pulmonary artery at 37; the lungs at 38 and the pulmonary vein at 39. The aorta is indicated at 41 while the vena cava is indicated at 42. The trachea indicated at 43 of course connects the nasal passage 44, shown in FIG. 3, to the lungs 33.

In FIG. 2 I show the catheter carrying the electrode 13 as being inserted in the right ventricle of the heart. This is accomplished by selecting, for instance, one of the major blood vessels of an arm and, by observing the patient through the fluoroscope threading the catheter into the heart proper until the electrode 13 is in position. With the patient anesthetized or sedated a suitable hydrogen mask is placed momentarily over the nose. The passage of hydrogen into the nasal passage results in giving a reading on the voltmeter 2% which indicates the amount of hydrogen, it being remembered that the electrode 22 located in the entrance to the nasal passage also is hydrogen sensitive. If there be a shunt such as indicated at 33 between the left ventricle 34 and the right ventricle 36, within a very short time, generally less than two seconds after inhalation, a reading is obtained on the voltmeter 29 which is indicative of the presence of hydrogen in the right ventricle 36. That is to say, were the shunt or defect 33 not present I have discovered that there will be a considerably longer time lapse between the inhalation of the hydrogen and its presence in the right ventricle 36. Therefore, by comparing the readings time-Wise on the two voltmeters 28 and 29 I can determine the length of time that it takes for the hydrogen to reach the right ventricle.

In actual practice I prefer to impress the signals from the electrodes 22 and 13 directly into the DC. input of an oscilloscope, D.C. amplifier, or potentiometer. However, because of the fact that the electrode 13 as well as the electrode 22 will, without amplification, develop as much as one hundred millivolts, amplification is not essential.

In FIG. 5 of the drawings I show in diagrammatic manner the circulatory system of the human body. My improved process and apparatus is adapted, by suitable manipulation of the catheter It to the diagnosis of the various shunts indicated in FIG. 5. In actual practice I have found that it is possible to place the electrode 13 very close to, for instance, a shuntsuch as 33 indicated in FIG. 2. Therefore, by suitable manipulation of the catheter, thus to change the location of the electrode 13, I can place the electrode 13 at the point of maximum concentration 'of'the hydrogen or other foreign and purposely injected or inhaled substance. By this means I amenabled to locate quite definitely the position of the defect in the septum. This is possible because the more concentrated the hydrogen in the blood passing through the defect, the greater the voltage on the instruments.

In FIG. 4 I show a series of'curves some of which were obtained from an actual patient having a septal defect. Iii these curves the vertical axes represent voltage, while the horizontal axes represent time in seconds. In each of these sets of curves the airway signal is the voltage curve resulting from the contact of hydrogen with electrode 22; the other curve of each set is the voltage curve resulting from the contact with electrode 13 of hydrogen carried by the blood in the various heart cavities. The following is given as an example of the technique used in the investigation where there is a suspected left to right shunt:

(l) The electrode 13 is inserted in the pulmonary artery. If a signal is obtained in about one second after inhalation of hydrogen this indicates a shunt some place. In this event the set of curves appears on the oscilloscope as shown at A in FIG. 4.

(2) The electrode is now withdrawn to lie the right ventricle and the patient is given another breath of hydrogen. In the event the set of curves appears as in 3, FIG. 4, which is a set of curves from a normal heart, this indicates that the shunt is not between the right and left ventricle, but is between the aorta and the pulmonary artery.

A second example of a technique is as follows:

(1) if, having placed the electrode 13 in the pulmonary artery, the signal obtained is abnormal, as in A of FIG. 4, then it will be found that the defect is likely to be in the right ventricle.

(2) By now placing the electrode 13 in the right auricle if a normal signal such for instance as that shown in the set of curves C of FIG. 4 is obtained, the defect must be in the right ventricle.

The foregoing examples serve to illustrate the techniques possible with my improved process and apparatus. In view of the fact that the catheter 13 may be inserted in practically any part of the heart proper, and because of the definite time and quantity relationship between the inhalation and appearance of hydrogen at the place'of location of the electrode, very accurate determinations may be made.

In each set of curves in FIG. 4 I designate the signal read from the voltmeter 28 upon the inhalation of hydrogen by the letter 0!. In each of the other curves of FIG. 4, I designate the signal produced by the cathode 13 and read on the voltmeter 29 by the letter e. In the several curves of FIG. 4 it will be noted that the curves may be plotted against equal increments of time such as seconds. Therefore, by correlating the time of the airway signal read on voltmeter 28 with the signal obtained from the electrode 13 and read on voltmeter 29, it is possible to determine very accurately the time lag between inhalation and appearance of the gas at the point under investigation. Incidentally, the determination of accurate placing of the electrode 22 may be checked by judging the appearance of the EGG obtained from it.

From the foregoing it will be apparent that I have .de

vised an improved process and apparatus for determining accurately and speedily the presence in the blood stream of living humans of a foreign substance purposely inhaled or injected for test purposes. In actual use my invention has proved to be extremely practical and satisfactory. In view of the fact that the test includes the breathing of one breath of hydrogen, it may be repeated It will thus be seen as often as once every two minutes. that the tests may cover a considerable length of time. In practice I find that the electrodes 13 and 22 should be replated after about every ten catheterizations. Furthermore, I have noted that electrodes made as herein disclosed, when in the presence of oxygen, tend to decrease the potential. That is, in a patient having a septal defect a stream of highly oxygenated blood, viz, arterial blood, passes through the defect to a place in the heart which normally contains blood of less oxygenation. By way of example the normal difference in voltage signal generated between arterial and veinous blood is approximately .01 volt. It is thus possible to use the technique and apparatus herein disclosed to determine changes in oxygen content of the blood in various parts of the body. An electrode constructed as herein shown and described has utility for such purposes as a pace maker electrode for hearts, or as an intracardiac EKG electrode.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications Without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

1. The process of det rmining the presence in the blood stream of a living human body of hydrogen in the blood comprising inserting directly into the blood stream a catheter borne electrode capable of generating an electric signal in the presence of hydrogen, and utilizing the signal thus produced to obtain an intelligible indication of the presence of such material in the blood stream adjacent the electrode.

2. The process of determining the presence in the blood stream of a living human body of hydrogen in the blood comprising inserting directly into the blood stream a catheter borne electrode capable of detecting a change in potential in the presence of hydrogen, and utilizing the signal thus produced to obtain an intelligible indication of the presence of such material in the blood stream adjacent the electrode.

3. The process of determining the presence in the blood stream or" a human body of material dissolved in the blood comprising inserting directly into the blood stream a catheter-borne electrode capable of generating an electric signal in the presence of such material, utilizing the signal thus produced by the electrode to produce an intelligible indication of the presence of such material adjacent the electrode, and comparing the signal time-Wise with an electric signal produced by the material as it is being placed in the blood stream.

4. The process of determining the presence in the blood stream of a living human body of material dissolved in the blood comprising inserting directly into the blood stream a catheter-borne electrode capable of detecting a change in potential in the presence of such material, utilizing the signal thus produced by the electrode to produce an intelligible indication of the presence of such material adjacent the electrode, and comparing the signal time-Wise with an electric signal produced by the material as it is being placed in the blood stream.

5. The process of detecting the presence of a substance at a given location in the blood stream of a living human body comprising placing a quantity of said substance in the blood stream at a location removed from said given location, inserting into the blood stream at said given location a catheter-borne electrode capable of generating an electric signal in the presence of said substance in the blood stream, and utilizing the signal thus obtained to indicate the presence of said substance at said given location.

6. The process of claim 5 including the further step of placing an electrode at the location Where said substance is placed in the blood stream, thereby to obtain :1 reference electric signal, and comparing time-Wise the two signals thus obtained, thereby to indicate the time of travel of the substance from the first location to the second one.

7. The process of determining the presence of hydro gen in the blood of living animals which comprises the steps of inserting into the blood stream an electrode capable of emitting an electric signal in the presence of hydrogen, introducing into the blood stream a quantity of hydrogen, and sensing the signal thus produced by the electrode, thereby to indicate the presence of hydrogen adjacent the electrode.

8. The process of detecting, localizing and determining the extent of arteriovenous shunts which comprises the steps of inserting in a possible shunt region of the circu latory system a catheter-borne electrode which produces an electric signal in the presence of a non-toxic substance in the blood stream, placing in the blood stream at a location opposite (in the sense of blood movement) the location of possible shunt a quantity or" said non-toxic substance, and sensing the signal produced by the electrode thereby to indicate the presence or absence of a shunt between the said locations.

9. The process of determining the presence of blood shunts in living humans which comprises inserting directly into the suspect portion of the heart a catheter-borne electrode capable of generating an electric signal in the presence of a purposefully inhaled non-toxic foreign gas, establishing an electric path from the electrode to the exterior of the body, sensing the signal from the electrode, producing an electric signal indicative of the amount of gas inhaled, and correlating the signals quantity-wise thereby to determine the extent of the shunt.

10. The process of claim 9 which comprises the further step of comparing the signals at regular intervals of time thereby to obtain an indication of the time required for the gas to reach the suspect part of the heart.

11. An intravascular electrode formed essentially of metals selected from the group consisting of platinum, palladium and blacks thereof and capable of generating an electric signal in the presence of hydrogen, an electric conductor electrically connected to the electrode and extending outwardly from the electrode and adapted to emerge at a point outside of a body into which the electrode is inserted, and means insulating the conductor from the body into which the electrode is inserted.

12. An exploratory catheter-borne electrode comprising an electrode proper capable of generating an electric signal in the presence of hydrogen, a catheter in the form of a small tube, means mounting the electrode on the entrance end of the catheter, an electric conductor electrically connected to the electrode and extending outwardly from the electrode and adapted to emerge from the catheter at a point outside of a body into which the catheter is to be inserted, and means insulating the conductor from the catheter.

References Qited in the file of this patent UNITED STATES PATENTS 1,933,791 Crouch Nov. 7, 1933 2,175,726 Gebauer Oct. 10, 1939 2,526,038 Nelson Oct. 17, 1950 2,675,493 Grobel Apr. 13, 1954 2,735,949 Podolsky Feb. 21, 1956 2,763,935 Whaley Sept. 25, 1956 2,816,997 Conrad Dec. 17, 1957 2,924,213 Fleck Feb. 9, 1960 2,949,107 Ziegler Aug. 16, 1960 2,949,910 Brown Aug. 23, 1960 2,976,865 Shipley Mar. 28, 1961 FOREIGN PATENTS 1,042,204 France June 3, 1953 OTHER REFERENCES Consolidated Leak Detector, received May 19, 1950, Model 24-101 A, 14 pages.

Journal of the Acoustical Society of America, pages 9-10, Jan. 1957.

Surgery, August 1958, pages 416-417. 

1. THE PROCESS OF DETERMINING THE PRESENCE IN THE BLOOD STREAM OF A LIVING HUMAN BODY OF HYDROGEN IN THE BLOOD COMPRISING INSERTING DIRECTLY INTO THE BLOOD STREAM A CATHETER BORNE ELECTRODE CAPABLE OF GENERATING AN ELECTRIC SIGNAL IN THE PRESENCE OF HYDROGEN, AND UTILIZING THE 